KR20160021220A - Miniaturized head for induction welding of printed circuits - Google Patents

Abstract

The present invention relates to an inductive head (1) for welding multi-layer stacks (48) to printed circuits or the like, wherein the inductor core (3) associated with the excitation inductance (6) Or other gaseous fluids. The second inductor core (4) cooperates with the first inductor core to induce magnetic flux in at least one junction region of the multilayer stack (48) interposed between the cores (3, 4); The cooling fluid surrounds the junction area of the multi-layer stack, thus enabling the separation of the head at the end of the welding process.

Description

≪ Desc / Clms Page number 1 > MINIATURIZED HEAD FOR INDUCTION WELDING OF PRINTED CIRCUITS < RTI ID =

The present invention relates to an inductive head for bonding intended layers to produce printed circuits.

For a better understanding of the present invention and the description of the invention that follows, it is worthwhile to provide a brief overview of the printed circuit production process to which the present invention is preferably applied.

As is known, printed circuits for electronic applications such as those used in computers (e.g., PCs), telephones, and other telecommunications equipment, appliances, machine tools, etc., And a plurality of conductive layers including tracks designed according to the topography of the circuit.

The production of the printed circuits can be accomplished by either printing on a project design or topography until the conductive sheets are assembled to produce so-called "multilayers ", which are stacks of laminates obtained by overlapping the alternating conductive layers of insulating layers. Lt; RTI ID = 0.0 > of the < / RTI > conductive sheets with the circuit tracks.

The insulating layers consist of a so-called "pre-preg ", that is to say that the synthetic fibers are used to form a single sheet with the stacked conductive layers, Insulating epoxy resins penetrated.

Printed circuits obtained by using this technique can be rigid like those commonly used in electronic boards or can be used for other applications such as for example the wired connection of components (PCs, etc.) of electronic computers, printers, copiers, Lt; RTI ID = 0.0 > a < / RTI > The thickness of the printed circuits can vary from a few tens of millimeters to a few millimeters.

Due to the development of customer computers and telecommunications technologies and equipment (Internet networks, mobile phones, laptops, tablets, satellite navigation systems, etc.), especially the latest generation of these, functions performed by electronic circuits It becomes increasingly complicated.

This requires higher performance levels without adversely affecting the lightness and portability of the devices, but on the contrary it evolves to tend to smaller sizes and thicknesses.

Producers are being forced to face this increasingly pressing need to minimize component weight; This translates into lighter, thinner components that withstand the technological advances, which increases the number of layers to be stacked to make so-called "multilayers ", while the thickness of their thickness . ≪ / RTI >

To provide an idea of the accompanying dimensions, the finished laminated sheet is about 1 millimeter thick and therefore the layers (at least one conductive layer with circuit tracks and one "prepreg" insulating layer) To a few tens of millimeters (typically 30-40 microns to 500-600 microns).

The manufacture of multilayer laminates is technically followed by much more difficult and accurate than in the past; In fact, the greater the number of layers to be stacked, the more accurately the other layer must be applied over one layer, otherwise the circuit will prove to be defective.

Consequently, if the single layers are only a few tens of microns thick, the overlapping tolerances will have the same degree of magnitude (i.e., microns).

The present invention is suitable for this technical context.

Indeed, the Applicant has previously developed a method for making stacks of multilayer laminates, including final compression and thermal bonding steps, with a suitable heating press.

In order to obtain printed circuit boards with desired final properties, i.e., specific structural and functional properties, it is necessary that the conductive and insulating layers overlap in the multilayer stack very precisely.

For this purpose, relative movements between the layers should be avoided during various multilayer stack processing steps; For this reason, it is known to make joints at various points of laminated layers to prevent laminated layers from moving, and thus the multilayer stack can be steered.

Recently, various welding techniques have been developed with approximately satisfactory results, which are based on the local heating of the multilayer stack; For example, machines have been made where the thermal energy required to make the junction is applied by electrodes heated by electrical resistors, or the irradiation energy is used in the form of microwaves or electromagnetic induction.

 For example, the Applicant has discovered that multi-layer stacks of printed circuits can be welded by using electromagnetic induction heads at various spots along the edges, according to the dimensions of the stacks of laminates that form the stack, International Patent Application No. PCT / IB2011 / 54486 on Machines.

For this purpose, the induction heads are provided with substantially C-shaped electromagnets, and the north-south poles of the electromagnets are arranged along a peripheral belt with metal spacers intended as passages for the molten resin, an individual of laminated laminates And operate at the edge points simultaneously.

These spacers occur in conductive layers that are crossed by electrical currents that generate the heat necessary to locally melt the (thermo-curable) resin that penetrates the insulating substrates when the induced magnetic field is applied to the conductive layers.

The locally hardened resin welds the layers at the locations of the spacers, thus ensuring the desired stable construction of the multi-layer stack, and can then withstand further processing steps.

The technique developed by the applicant provided very interesting results; Therefore, it is an object of the present invention to further develop it.

For this purpose, it would be desirable to be able to use it in multiple junction spots, in order to be able to achieve better results; As will be readily appreciated, in practice, if laminated layers are welded in multiple spots along their edges, better bonding will be achieved because the spots will be more evenly distributed with respect to the stack of laminates, It is also safer because joints will still be guaranteed by other spots which are more and closer to each other than can be achieved as a conventional machine if one joint spot is defective.

In view of the above description, it is believed that the technical problem underlying the present invention is to provide a method and system for inducing junctions of stacked layers intended for the production of printed circuits in spots closer to each other, in order to obtain better uniformity and reliability of the junction as a whole. It may be mentioned to provide a welding head.

The idea to solve this problem is to provide a smaller induction head than known ones; In practice, this allows the use of a greater number of heads dispersed along the edges of the laminated laminations, in order to weld laminated laminates in corresponding spots.

According to the invention, the induction heads are advantageously cooled so that their dimensions can be reduced; The ferromagnetic material heated by the induced induction during the welding process will still operate at temperatures that allow the head to work properly under the conditions required to form the junction.

The features of the induction head according to the present invention appear in the claims appended hereto.

The advantages derived from these features and features as well as the advantages of the present invention will become more apparent from the following description of an example embodiment of the invention as illustrated in the accompanying drawings, which are provided by way of non-limiting example.

1 is a perspective view of an induction welding head according to the present invention.
Figure 2 shows the welding head of Figure 1 with a part of it removed.
Fig. 3 shows details of the welding head of Figs. 1 and 2. Fig.
Figure 4 shows the details of the welding head of Figure 3 with a part of it removed.
5 is an enlarged view of a part of the details of Figs. 3 and 4. Fig.
Figure 6 shows an application of an induction head according to the invention.
Figure 7 shows details of the ferromagnetic element used in the application of Figure 6;

Referring to the above listed drawings, Figure 1 shows a schematic view of an induction head 1 according to the present invention, which comprises an outer structure 2 which houses a first inductor core 3 made of a ferromagnetic material and which is substantially C- Fig.

The inductor core 3 supports the excitation inductance or coil 6 and is magnetically coupled to the second inductor core 4.

Both of the inductor cores 3 and 4 are connected to the inductance 6 when the inductance 6 is excited by an alternating current having a frequency of several kHz, preferably between 18 kHz and 30 kHz, Lt; RTI ID = 0.0 > fluxes < / RTI >

The material permeable to the magnetic flux used to make the inductor cores is preferably ferrite: by using ferrite it is possible to limit the parasitic currents induced by the variable magnetic flux, without resorting to lamination of the core material .

If a simple ferromagnetic material is used (e.g., soft iron), such parasitic currents may cause the cores 3 and 4 to overheat unless the cores 3 and 4 are provided in the form of sheet stacks such as transformers something to do.

The first inductor core 3 preferably includes two parallel arms 12a, 12b that are C-shaped or U-shaped and extend from the central body 12c; An inductance 6 is wound on the central body 12c and the inductance 6 is made up of a relatively small body of between 20 and 35, preferably 30, made of conducting material (e. G., Copper or alloys of copper) Has a number N of loops, and consists of a coil having a circular cross section with a diameter for a particular application.

According to a preferred embodiment, the conductors are wound on coils 6 on concentric loops of two or more orders, and thus do not increase the length of the first ferromagnetic core 3, To obtain corresponding coaxial coils wound around the central body 12c.

This reduces the overall dimensions of the induction heads 1 along the edges of the layers to be welded. In addition, this provides a higher induction level, and the length of the inductor core 13 and other conditions (supply voltage and current, cross section of the wound conductor, etc.) are the same.

The upper end face 13 of the central body 12c of the inductor core 3 has a cylindrical shape like the other core portions in order to prevent the overlapping winding orders of the loops from excessively increasing the diameter of the coil 6. [ It is preferably flat.

According to a preferred embodiment of the invention, the welding area and / or inductor coil 3 is cooled.

For this purpose, there are grooves 30, 31 extending longitudinally on the outside of the arm along the arms 12a, 12b; The grooves are used to blow air into the structure 2 housing the ferromagnetic core 3 through the holes 32 and 33 and the collector channel 34 of the upper portion of the structure 2 Is used.

The collector channel 34 preferably has two portions, namely a first portion 20, preferably comprising a cavity 21, a first portion 20 being a conjugate of the shape of the inductor core 3, and Shaped second portion 22 which acts as a face to close the first portion 20 and the second portion 22 is secured to the first portion 20 by means of screws or the like , Which are not shown in the figures because they are known per se.

The collector 34 is connected to air supply tubes (not shown in the figures) of the machine in which the welding head 1 is installed.

The airflow enters the enclosure 2 through the holes 32 and 33 and flows along the longitudinally extending grooves 30 and 31 in the enclosure and then flows through the end sections of the arms 12a and 12b Coming out from the fields; In this way, the heat can be removed from the area most affected by thermal stress during the multi-layer welding cycle, thereby improving the reliability of the process, even with smaller induction heads and all other conditions, such as supply voltage and current, The thickness of the multilayer to be welded and the like are the same.

For these purposes, the air flow rate, the air temperature and other parameters affecting the welding process are controlled and managed by the machine's control system as described below.

The smaller size of the induction head will also reduce the heat exchange area between the inductor core 3 and the multi-layer zone to be welded: therefore it will not be possible to use the same supply current and voltage.

The cooling of the head 1 according to the invention, however, allows to maintain the same operating parameters in order to obtain the required induction by the welding process without the risk of reaching excessive temperatures which can damage the material locally .

Indeed, the higher the required power, the larger the cross-section of the conductor and inductor core 3; It should also be pointed out that the supply current will vary from 10 to 14 amperes, with a voltage in the range of 300 to 560 volts, depending on the number of loops and the type of induction head, as will be explained below.

The free ends of the two arms 12a and 12b of the inductor core 3 have opposite polarities so that the flux produced by the inductance 6 is the sum of the flux generated by the inductance 6, If any, will develop along a magnetic circuit extending from the first inductor core 3 to the second inductor 4 while crossing the air gap therebetween.

In this example, the second inductor core 4 is made of a bar or a plate made of the same material (ferrite) as the first inductor core; The thickness and dimensions of the plate are proportional to the magnetic flux circulating in the circuit.

According to a preferred embodiment, the width of the second inductor core 4 is greater than the width of the first core 3, which is preferably 2 or more Can be used as the magnetically associated element with respect to the heads 1 of the magnet.

For this purpose, the cross section of the second core 4 should be greater than or equal to the cross section of the first core 3, in order to enable the passage of the magnetic flux, as will be explained further below.

Preferably, the metal platelets 40, 41 are present at the points juxtaposed to the ends of the arms 12a, 12b of the first core 3 on the second core 4.

Such small plates are made of copper or other electrically conductive material and heated through the effect of the currents induced therein, so that the temperature is similar to the temperature of the multilayer stack of laminates and promotes the welding action; Advantageously, deposits or scales of molten resin originating from "prepreg" insulating layers, which can reduce the efficiency of the system, are formed on the small plates 40,41 and on the second core 4 Strips 42 of the plastic film are applied on the second core 4 to prevent it from being damaged.

It should be noted, however, that the small plates 40, 41 may alternatively be applied on the ends of the arms 12a, 12b of the first core 3 instead of the second core 4.

The inductive head 1 according to the present invention allows stacks 48 of overlapping layers to be welded to be welded including insulating layers 50 alternating conductive layers 49, And the insulating layers 50 are made of the above-mentioned prepregs.

In addition, conductive layers 49 have peripheral belts 52 in which conductive spacers 55 are arranged; The conductive spacers 55 are elements made of an electrically conductive metal material (e.g., copper), the thickness of which is substantially the same as the thickness of the printed circuit 51 and therefore varies from a few tens of millimeters to a few millimeters can do.

Spacers 55 may have a circular, elliptical, polygonal (quadrilateral, hexagonal, etc.) or mixed shape, distributed evenly (with ordered rows, in a matrix or with a five-eye pattern, etc.); These areas can vary from 3 to 30 mm < ² > and are preferably evenly spaced at a distance of about 1-2 millimeters.

In this way it is possible to obtain a buffer zone or belt 52 along the edge of the conductive layers 49 consisting of a plurality of evenly spaced spacers 55: the width of the belt is in the range of 4-5 centimeters to 1 Cm < 2 > or less.

It should be noted that layers 49 and 50 of stack 48 do not have short circuit loops or other equivalent elements arranged in predetermined regions and are present in the prior art multilayer stack in contrast. Therefore, the welding heads 1 according to the present invention can be arranged at any point along the sides of the multi-layer stack 48 to make the joint, as described below.

The sheets 49, 50 forming the multi-layer stack 48 are stacked precisely with the help of suitable centering devices or holders, as is already known in these applications.

The prepared multilayer stack 48 is provided with its own buffer belt 52 interposed between each welding head 1 and the second inductor core 4 associated with the welding head 1 The heads may be arranged in any position with respect to the multi-layer stack 48, since the joints can be made at any point of the buffer belt 52 in accordance with the present invention.

However, it will be appreciated that it is generally desirable to have a homogeneous distribution of joint spots along the edges of the stack 48 in order to obtain a stronger junction and a more stable configuration; Therefore, the inductive heads 1 will generally be evenly distributed along the edge of the multilayer stack 48.

In this regard, it should be noted that at the beginning of the operating cycle, the inductor cores 3 and 4 of each head 1 are spaced apart to allow insertion between the multi-layer stacks 48, Have; However, the distance between the cores 3 and 4 is individually adjusted to be in contact with the top and bottom surfaces of the multi-layer stack 48. For this purpose, the machine on which the induction heads 1 are mounted has its own means for adjusting the distance between the cores 3 and 4, such as, for example, screw mechanisms, hydraulic cylinders,

Power can be supplied to the inductance 6 of each head 1 to create an induction in the first core 3 and then the multilayer stack is inserted into the air gap 46 ) And a second inductor core (4).

The magnetic fluxes coming from one of the poles 12a and 12b of the first core 3 will not laterally spread out and cross the second core 4 and then laterally enter the other pole of the same core, The multi-layer stack 48 to be welded will therefore be identical to the flux from one of the poles of the inductor core 3 due to the particular construction of the welding head 1, , It is crossed across its thickness by the magnetic flux at two distinct points in the same way.

In addition, the AC power source of the inductance allows to periodically invert the signs N and S (+ and -) of the polarities of the first inductor core 3, so that an optimum balance of the system conditions is achieved under normal operating conditions .

In this condition, in the spacers 55 crossed by the high frequency alternating magnetic flux (18 to 30 kHz) supplied to the inductance 6, parasitic currents are induced, which causes local heating of the conductive layers 49, The resin into which the prepreg insulating layers 50 can be infiltrated can be cured, thereby providing the desired bonding.

In accordance with a preferred embodiment of the present invention, during the application of magnetic induction, i.e. when power is supplied to the coil 6, the air flow along the grooves 30, 31 is used to enable local heating of the spots to be welded At least partially. In this context, it is necessary to emphasize the importance of having a plurality of discrete elements, i. E. Spacers 55 crossed by a uniform magnetic flux.

Indeed, the induced magnetic fluxes to which the spacers are associated are coincident, i. E. Positive or negative, depending on the AC cycles of inductance 6; In addition, the spacer elements 55 are small compared to the cross-sections of the inductor cores 3 and 4 and are on average 10 to 20 times smaller, so that the fields flowing through the spacer elements 55 are substantially constant for each of them .

Also, once the resin is melted and dispersed, all flux induced in the cores 3 and 4 will flow through the multi-layer stack 48 because all flux is fully associated with the multi-layer stack 48; In other words, it should be emphasized that the vector sum of the magnetic field flowing through the multilayer stack 48 is equal to zero.

This increases the efficiency of the inductive head 1 because the stack 48 can be welded at multiple spots in the positions of the two arms 12a, 12b of the magnetic core 3 of each head .

The result is also made possible by the fact that the flux intensity is the same (although with opposite signs) in the joint spots, since the geometry of the system is symmetrical.

This allows to have the same operating conditions (temperature, induced currents, etc.) for each welding head 1, since the magnetic field is the same: it is therefore possible to control the welding process in multiple spots , It is not possible with prior art welding heads which can only be welded in one spot in contrast.

This effect is advantageously exploited in the embodiment of the invention shown in Figure 6 in which a single second ferromagnetic core 4 is associated with two first cores 3 supporting individual induction coils 6 do.

With this solution, welding in close spots of the multilayer stack can be possible in a balanced manner; For this purpose, according to a preferred arrangement, the induction coils 6 of the heads 1 associated with one identical second core 4 are connected to one another in series or in parallel so that the coils operate by the same current And the magnetic induction produced by the induction coils 6 of the individual cores 3 and 4 will be the same.

During the welding process, the heads 1 are also advantageously provided with air or other suitable gas (e. G., Air) flowing along the grooves 30 and 31 extending from the arms 12a and 12b of the first core 3 For example, nitrogen, CO ₂ ).

In practice, the air or gas flow is also required to maintain the temperature of the head 1 within reasonable values to ensure proper and reliable operation, and furthermore to accelerate the curing of the resin of the insulating layers 50, thus reducing the duration of the welding process, 48) of the head (1).

In this regard, it is also noted that it is advantageous to apply a downward force on the multi-layer stack 48 under the pressure exerted by the airflow exiting the grooves 30, 31 to advantageously assist in multi-layer stack separation from the induction head 1 .

In other words, it can be said that the aeration system of the induction head according to the invention has a double effect: on the one hand, it is possible to maintain the temperature within predetermined limits even in the presence of a smaller induction head Welding parameters, e.g., applied magnetic induction, voltage and current are the same); Which on the other hand helps to separate the multilayer stack from the induction head at the end of the curing and welding process of the resin.

In this regard it should be emphasized that the enclosure 2 of the induction head 1 is open at the ends of the arms 12a and 12b of the inductor core 3 and thus allows circulating air or other gases to exit ; This aspect distinguishes the head 1 from known heads with fixed magnetic poles in which a shielding or protective platelet is generally applied (which would prevent air from flowing out according to the invention).

How the induction head 1 can solve the technical problem dealt with by the present invention can be easily understood from the above description.

In effect, this allows the multi-layer stack 48 to be welded at any spot along the buffer belt in which the conductive spacers 52 are arranged, thus allowing a much greater number of joint spots than in the prior art: Is due to the head according to the present invention having the same conditions but smaller than prior art heads, and thus a larger number of such heads can be used along the edge of the multilayer stack. This effect can also be described in more detail by the arrangement of the invention in which two or more cores 3 supporting individual induction coils 6 are magnetically associated with one and the same core 4 : This arrangement actually makes better use of the available spaces in terms of both the accessibility of the joint spots along the multilayer stack and the ability to achieve favorable synergies to power and cool the inductive heads.

As can be appreciated, in practice, a closer arrangement of the cores supporting the coils 6 enables their electrical connection through the same conductors, leading to simpler electrical connections; In addition, according to the preferred embodiment, since the series connection of the power coils 6 is achieved by providing a synergy induction effect between the coils, which maximizes the flux of the junction spots at the ends of the arms 12a, 12b It has been verified that it will be preferable.

For this reason, according to a preferred variant of the invention, the coils are wound in opposite directions on the respective central elements 12c of the core: this is achieved by maximizing the induction effect and, therefore, The goal is to synchronize the individual fields of the mutual induction with the fields generated by the flowing current.

Also, the supply of air to cool the welding heads can also be used to separate the individual coil support cores (e. G., Compressors) since the individual grooves 30,31 can be all connected to the same source 3). ≪ / RTI >

In this regard, it should be noted that preferably the distance between the grooves of the arms 12a, 12b of the core in the heads 1 according to the invention is less than 10 ÷ 15 centimeters; In addition, the minimum distance between the two coil support cores 3 associated with the same inductor core 4 is at least about 1 cm. There may also be more than two cores 3, which are arranged side by side and support coils 6 magnetically associated with one identical second inductor core 4, in accordance with the principles of the present invention It should be noted.

Of course, the present invention can be influenced by many variations only to some extent with respect to the description provided.

For example, to increase the flow of cooling air, more grooves 30, 31 may be present on the arms 12a, 12b of the first inductor core 3; Consider, for example, a series of grooves parallel to those shown in the Figures, distributed at predetermined angular pitches along the arms.

Likewise, the linear shape of the grooves 30, 31 can be replaced by a curved or spiral configuration, although it is preferred because it can be easily obtained by mechanically machining (e. G., Milling) the core 3; This is the case where the grooves extend spirally along the arms 12a, 12b.

As a further possible modification of the invention that may be considered, grooves for cooling air flow may be provided in the second ferromagnetic inductor core, i.e. one inductor core does not support the coil.

It should be emphasized more generally that some of the structure and / or functional aspects of the head 1 may be reversed when compared to the example described herein.

To further clarify this aspect, consider that the positions of the inductor cores 3 and 4 may be reversed; Therefore, it will not prevent the inductor core 3 supporting the coil from being arranged under another inductor core 4; The other inductor core 4 is similar to the above-mentioned grooves 30, 31 and can be provided with grooves for the fluid to cool the welding area.

Further, although in the example contemplating the present application, other solutions are contemplated, even though air flows freely along the grooves 30 and 31, i.e., the grooves are used to transfer air from the collector 34 to the welding area It should be noted that air is supplied by the tubes housed in the grooves 30, 31 and extending from the collector 34 to the weld zone.

In other words, using these tubes, the air can be made from tubes, which themselves can be made of metal, plastic or other suitable material, and are housed in grooves 30, 31 that exchange heat with the ferromagnetic inductor core 4 Therefore, it will not be in direct contact with the core 2.

Further variants of the invention may relate to the arrangement of the inductor cores 3 supporting the coils 6; In practice, reference is made to the core 3 arranged in the individual housing enclosure 2 for the sake of simplicity in the examples shown in the figures.

However, variants are conceivable, in which two (or more) parallel inductor cores 3 are housed in one of the larger enclosures 2 in the same enclosure 2: (Or more) inductors with respect to the workpiece 48, the application of the inductors to the welding machine is simplified.

Finally, although air has been referred to herein as the cooling fluid flowing in the induction head 1, it has been found that this is not the case for other gases (preferably carbon dioxide, nitrogen or inert gases, or even inert gases such as gases for industrial use) It should be noted that it is easy to understand that it is a simple and inexpensive solution that does not rule out use.

All of these variations will still fall within the scope of the following claims.

Claims (13)

1. An inductive head (1) for welding multi-layer stacks (48) for printed circuits,
A first inductor core (3) associated with excitation inductance (6); A magnetic core cooperating with said first core (3) to guide at least one junction region of a multi-layer stack (48) interposed between said first inductor core (3) and a second inductor core (4) 2 inductor core 4,
The induction head (1) comprises a path (30, 31) for a cooling fluid extending along at least one of the first inductor core (3) and the second inductor core (4)
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. The method according to claim 1,
Wherein the path of the cooling fluid extends to at least the junction region and the fluid surrounds the multi-layer stack (48) interposed between the first inductor core (3) and the second inductor core (4)
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 3. The method according to claim 1 or 2,
Wherein the path of the cooling fluid comprises at least one groove (30, 31) formed in an individual inductor core (3, 4)
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 4. The method according to any one of claims 1 to 3,
Is associated with individual inductances (6) to guide the flux towards the corresponding junction regions of the multilayer stack (48) interposed between the first cores (3) and the second core (4) And at least two said first inductor cores (3) cooperating with an inductor core (4)
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 5. The method of claim 4,
The inductances 6 are wound in opposite directions on the individual cores 3 to adjust the magnetic fluxes individually associated with the individual cores in a manner for maximizing the flux through the multilayer stack 48 losing,
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 6. The method according to any one of claims 1 to 5,
Wherein said first core (3) is housed in an enclosure (2) in which said at least one junction region is substantially open, so that a cooling fluid flows between said first core (3) and said second core Layer stack,
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 7. The method according to any one of claims 1 to 6,
(40, 41) arranged on said first and / or second cores (3, 4) at junction regions of said multilayer stack (48)
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 8. The method according to any one of claims 1 to 7,
The first inductor core 3 is made of a magnetically permeable material and includes a substantially C-shaped body, and the pair of terminal arms 12a, 12b are formed such that the inductance 6 is formed by a magnetic flux, Extending from the associated central portion 12c for guiding to the first and second portions 12a, 12b,
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 9. The method of claim 8,
Grooves 30 and 31 extend along the arms 12a and 12b of the first inductor core 3 for passage of the cooling fluid.
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. 10. The method according to any one of claims 1 to 9,
The second inductor core (4) comprises a substantially straight element made of a ferromagnetic material.
An inductive head (1) for welding multi-layer stacks (48) for printed circuits and the like. A method for welding multi-layer stacks (48) to printed circuits,
The at least one electrically conductive layer 49 is deposited on at least one electrically insulating layer 50 into which resins or similar thermomelting materials are impregnated,
At least one first inductor core (3) associated with one inductance (6) and a second inductor core (3) cooperating with the first inductor core (3) to guide the magnetic flux into at least one junction region Interposing a multi-layer stack (48) between the substrate (4);
Ii) supplying an alternating current to the inductance for a time period sufficient to ensure local melting of the resin in the junction region 52;
Iii) blowing cooling fluid toward the bonding region 52 for a time sufficient to cure the previously melted resin;
Iv) moving the first inductor core (3) away from the multi-layer stack (48)
/ RTI >
A method for welding multi-layer stacks (48) to printed circuits. 12. The method of claim 11,
The cooling fluid is a gaseous fluid, preferably air,
A method for welding multi-layer stacks (48) to printed circuits. 13. The method according to claim 11 or 12,
The bond region is arranged on the peripheral belt (52) of the multi-layer stack (48) with the conductive spacer elements (55)
A method for welding multi-layer stacks (48) to printed circuits.

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